The invention relates generally to the area of magnetizers. More specifically, the invention relates to the area of magnetizers for magnets that are disposed in-situ within a mechanical member, such as a rotor of an interior permanent magnet machine.
The rotors of many electric machines include permanent magnets that produce magnetic field flux, which magnetic field flux interacts electromagnetically with a stator. The electromagnetic interaction results in a conversion of electromagnetic energy to mechanical energy within the electric machine.
Interior permanent magnet electric machines constitute a class of electric machines in which the permanent magnets are buried within the bulk of the rotor. In an as-formed state, the permanent magnets do not have any net magnetic moment. However, design principles of the electric machines require that the permanent magnets disposed within the bulk of the rotor be in a magnetized state before the electric machine can be put in operation.
Two approaches to the processes of magnetization and assembly of permanent magnet electric machines are known within the art. In the first approach, the permanent magnets are magnetized before they are disposed within the bulk of the rotor. This approach presents several drawbacks from the point of view of an industrial assembly process for electric machines. For instance, it will be appreciated that fully magnetized permanent magnet pieces would be subject to electromagnetic interaction with all surrounding objects, which in turn adds to the complexity of their handling procedures. In the second approach, the as-formed permanent magnets are disposed within a rotor and a magnetizer is used to magnetize the permanent magnets.
The second approach also presents several drawbacks from the point of view of an industrial assembly process for electric machines. For instance, the energy and fabrication costs for magnetizers capable of generating, at the location of the permanent magnets, a magnetic field flux sufficient to magnetize the permanent magnets, are prohibitive. Typical prior art in-situ magnetizers are able to economically magnetize permanent magnets made of materials or grades, such as alnico and ferrite, that have low intrinsic coercivity. Such prior art in-situ magnetizers also find limited use for magnetizing surface mounted permanent magnets. Many emerging applications for permanent magnet electric machines, such as wind turbine applications, or traction applications, would benefit from the use of high-coercivity rare-earth permanent magnet materials. In-situ magnetization of such high-coercivity rare-earth permanent magnets is not economically feasible via prior art in-situ magnetizers.
A magnetizer that is capable of economically providing user definable magnetic flux field configurations at the locations where the permanent magnets for example, high-coercivity rare-earth permanent magnets, are disposed within a mechanical member, for example a rotor, and having a design that is readily adaptable for electric machines of different sizes and configurations, would therefore be highly desirable.